The present invention generally relates to medical devices, and more particularly, to methods of assembling catheter tips with sensors.
Catheters are widely used in the medical arts. For example, catheters are sometimes inserted into a patient""s body during mapping and ablation procedures of the patient""s heart. Catheters used for such procedures typically comprise of electrode tips and electrode rings. Various other components may also be incorporated into these medical catheters. For example, a steering mechanism allowing the physician to control the movement of the catheter while the catheter is in a patient""s body may be incorporated into the catheter. A thermistor or a thermocouple may also be placed at the catheter tip to provide temperature data. In addition, such catheters may incorporate other sensors at the tip to assist the physician in performing these delicate procedures.
One type of sensor currently being incorporated into catheter tips is an electromagnetic sensor, which provides important information to the physician about the exact location of the catheter tip relative to the patient""s body. An electromagnetic sensor used for such purposes and commercially available is a xe2x80x9c3Dxe2x80x9d sensor, which employs an orthogonal arrangement of three sensor pairs to provide three-dimensional position coordinates of the catheter tip. Details on the structure and use of a xe2x80x9c3Dxe2x80x9d sensor are discussed in PCT publication WO 00/10456, entitled xe2x80x9cIntrabody Navigation System for Medical Applications,xe2x80x9d which is hereby expressly and fully incorporated herein by reference.
Incorporating such sensors into catheter tips during assembly can be difficult. Catheters used in, for example RF ablation and mapping procedures, tend to be very small in size, thus requiring assembly techniques that must be precise. In addition, electromagnetic sensors are highly sensitive to excess thermal energy and magnetic fields. Even short exposure to excess thermal energy and magnetic fields may cause damage to these sensors.
Thus, the assembly of distal catheter assemblies that contain electromagnetic sensors are further constrained, since certain heat generating steps, for example soldering, may potentially expose these sensors to excess heat. Further, many of the components incorporated into these devices are made from ferrous material, such as stainless steel, which can magnetically affect the sensors. Thus, a method for assembling a distal catheter assembly without damaging a magnetic and heat-sensitive component contained therein would be highly desirable.
The present inventions include distal catheter assemblies, catheters, and methods that minimize damage to sensitive components.
In accordance with a first aspect of the present inventions, a distal catheter assembly comprises a composite housing that includes a distal member having a distal cavity formed therein, and a separate proximal member having a proximal cavity formed therein. By way of non-limiting example, the composite housing may form a cap-shaped head and a cylindrical neck. In this case, the head may form an ablation electrode, and ring electrodes, such as mapping electrodes, may be disposed around the neck. A channel may be formed distal to the cavity, where a thermistor can be disposed. The entirety of the cap-shaped head may be formed by the distal member, and the entirety of the cylindrical neck may be formed by the proximal member. Alternatively, one of the cap-shaped head and cylindrical neck may be formed by both of the distal and proximal members, and the entirety of the other of the cap-shaped head and cylindrical neck formed by either the distal member or proximal member.
The distal catheter assembly further comprises a first component, such as a sensor, mounted within the distal cavity. The distal catheter assembly further comprises a second component mounted on the proximal member. The second component can be, e.g., a steering assembly, and if the housing comprises an ablation electrode, an RF lead. Optionally, if the proximal member is hollow, it may include an open window through which the inner surface of the proximal member can be accessed. For example, if the second component is soldered to the inner surface of the neck, the open window may provide a working space for the soldering iron. The open window can be formed by, e.g., providing a cutout in the neck.
In accordance with a second aspect of the present inventions, a method for assembling a distal catheter assembly comprises providing a distal member and a proximal member. By way of non-limiting example, the distal member can form an ablation electrode, in which case, the distal member can include a channel, where a thermistor can be optionally mounted therein. The method further comprises mounting a first component, such as a sensor, within either the distal member or the proximal member by a suitable means, such as potting. The component can be inserted into the distal member by front-loading it through a proximal opening therein, or can be inserted into the proximal member by back-loading it through a distal opening therein. The method further comprises mounting another component, such as a steering assembly or RF wire, on the proximal member by suitable means, e.g., heat generation, and more specifically, soldering.
The method further comprises affixing the proximal member to the distal member, e.g., by affixing either the distal end of the proximal member within the proximal end of the distal member or the proximal end of the distal member within the distal end of the proximal member, e.g., by means of bonding or a threaded arrangement. Thus, since the second component does not come into contact with the proximal member until after the first component is mounted thereon, any adverse effects on the first component that may otherwise result can be minimized or completely eliminated.